Bearing Suffix Decoder: What Z, ZZ, 2RS, C3, E, M, and the Rest Mean
A bearing part number like 6213E-Z or 6205-2RS1-C3GJN looks like alphabet soup. Each letter cluster encodes a specific physical attribute — what kind of seal, how loose the internal fit is, what the cage is made of, whether it's been modified for high-speed or insulated for an electric motor.
This guide decodes every common bearing suffix you'll encounter, with worked examples for the part numbers you're most likely to look up.
How a Bearing Part Number Is Structured
Most industrial bearings follow a pattern: a base part number that defines size and type, followed by suffix codes that modify the design.
Take 6213E-Z as an example:
| Position | Value | Meaning |
|---|---|---|
| 1st digit | 6 | Bearing type — deep groove ball |
| 2nd digit | 2 | Width series — light (62-series) |
| 3rd–4th digit | 13 | Bore code — multiply by 5 for mm bore (65mm) |
| Suffix | E | Internal design modifier — enhanced design |
| Final suffix | Z | Shield/seal designation — single metal shield |
The base part number (6213) defines size and bearing type. Everything after it modifies the design — seals, clearance, cage material, internal geometry, precision class.
For a deeper dive on the base part number structure, see How to Read a Bearing Part Number. This guide focuses on what comes after.
Shields: Z and ZZ
Shields are thin metal plates pressed into the outer ring with a small gap to the inner ring. They keep large particles out and grease in but aren't fully sealed.
| Suffix | Meaning | Notes |
|---|---|---|
| Z | Single shield | One side shielded, one side open |
| ZZ / 2Z | Double shield | Both sides shielded |
ZZ and 2Z are the same thing — different brands write it differently. Both mean shields on both sides.
Shields run cooler than seals because there's no contact friction. They're the right choice for clean, high-speed applications like electric motor drive ends or HVAC fan bearings.
Worked example: 6205-ZZ is a deep groove ball bearing with double metal shields. See /bearing/6205-ZZ.
Seals: RS, 2RS, 2RS1, RSR
Seals are rubber lips that contact the inner ring directly, creating a full seal. They run hotter than shields but block fine dust and moisture.
| Suffix | Meaning | Brand notes |
|---|---|---|
| RS | Single rubber seal | One side sealed |
| 2RS | Double rubber seal | Generic / Timken convention |
| 2RS1 | Double rubber seal | SKF-specific (nitrile rubber) |
| 2RSR | Double rubber seal | FAG-specific (heavy-duty) |
| DDU | Double rubber seal | NTN-specific |
| LLU | Double rubber seal | NTN alternative |
All the "2RS-family" suffixes describe the same physical configuration. The letter difference is a brand convention, not a design difference. A SKF 6205-2RS1 and a NTN 6205-LLU are dimensionally and functionally identical.
For a fuller treatment of seals specifically, see What Does 2RS Mean on a Bearing?.
Worked example: 6205-2RS1 is a deep groove ball bearing with double rubber seals (SKF designation).
Clearance Classes: C2, CN, C3, C4, C5
Internal clearance is the small amount of play between the rolling elements and the races before the bearing is loaded. The clearance class is set when the bearing is manufactured and matters when the bearing will run hot, be pressed into a tight housing, or be subjected to thermal expansion.
| Suffix | Clearance | When to use |
|---|---|---|
| C2 | Reduced | Precision applications where minimal play is needed |
| CN | Normal | Default — usually shown as no suffix at all |
| C3 | Increased | Hot-running motors, high-speed applications, tight housings |
| C4 | Greatly increased | Severe heat, high thermal expansion environments |
| C5 | Extremely increased | Rare; specialty applications |
C3 is by far the most common non-standard clearance you'll encounter. Electric motor bearings are almost always specified C3 because the inner ring expands when the motor heats up. If the clearance were normal, the bearing would seize as it warmed.
Clearance is independent of seal type. A bearing can be open, shielded, or sealed in any clearance class — they're separate dimensions of the spec.
Worked example: 6205-2RS1-C3 is a sealed deep groove ball bearing with increased internal clearance — common for electric motor applications.
Cage Materials: M, TVH, J
The cage holds the rolling elements evenly spaced. The default cage material on small bearings is steel, but high-temperature, high-speed, or heavy-duty applications often specify something different.
| Suffix | Cage material | When you'll see it |
|---|---|---|
| (none) | Pressed steel | Default for most ball bearings |
| M / MA / MB | Machined brass | Heavy-duty, high-temp, vibration-prone applications |
| TVH / TVP / TVPB | Polyamide (nylon) | Lightweight, mid-temp, lower-noise applications |
| J | Pressed steel | Some manufacturers spec this explicitly |
Brass cages are common on spherical roller bearings and large cylindrical rollers because they handle higher temperatures and shock loads better than steel.
Worked example: 22210EM is a spherical roller bearing with E (enhanced design) and M (machined brass cage).
Internal Design Modifiers: E, CM, GJN, HC5
These suffixes describe modifications to the bearing's internal geometry or materials.
| Suffix | Meaning |
|---|---|
| E | Enhanced internal design — more or larger rollers, higher load capacity |
| CM | Controlled clearance for electric motors |
| GJN | Insulated bearing for electric motor applications (prevents electrical erosion) |
| HC5 | Hybrid bearing with ceramic balls |
| VV | NTN double non-contact rubber seal |
| EX | NSK enhanced internal design |
The E suffix is standard on most modern cylindrical roller bearings. NU309E has more rollers than the older NU309 design, giving it higher dynamic load capacity at the same dimensions.
The CM designation appears on motor bearings where both the seal and the clearance have been controlled for electric motor service. It's not a separate clearance class — it's a "this bearing was specifically designed for motor service" flag.
GJN is a specialty insulation that prevents shaft current from arcing through the rolling elements. Critical for variable-frequency drive (VFD) motors where shaft voltage can damage standard bearings.
HC5 (and similar hybrid designations) means the rolling elements are ceramic instead of steel. Used in high-speed, high-temperature applications like machine tool spindles and EV traction motors.
Worked example: NU309E-M is a cylindrical roller bearing with enhanced internal design and a machined brass cage.
Precision Classes: P0, P6, P5, P4
Most bearings are made to standard precision (P0). Higher precision classes have tighter tolerances on bore, OD, and runout.
| Suffix | Precision class | When to use |
|---|---|---|
| (none) / P0 | Normal | Default for general industrial applications |
| P6 | Higher precision | Slightly higher accuracy applications |
| P5 | ABEC 5 equivalent | High-precision applications |
| P4 | ABEC 7 equivalent | Machine tool spindles, high-precision rotation |
| P2 | ABEC 9 equivalent | Extreme precision; rare |
You'll see precision class on machine tool spindle bearings, high-end pump bearings, and instruments. For most maintenance and replacement work, the bearing's precision class will already be specified by the OEM.
Decoding Real Part Numbers
Two examples that show how the pieces combine.
6213E-Z
6 - Deep groove ball bearing 2 - Light series (62) 13 - Bore code (13 × 5 = 65mm bore) E - Enhanced internal design Z - Single metal shield
A 65mm-bore deep groove ball bearing with enhanced design and a metal shield on one side.
6213ZZCM
6 - Deep groove ball bearing 2 - Light series (62) 13 - Bore code (65mm bore) ZZ - Double metal shield CM - Controlled clearance for electric motors
Same base bearing as the example above, but with shields on both sides and clearance specifically tuned for motor service. This is a more application-specific bearing — the OEM spec'd CM because it's going into a motor where thermal expansion needed to be accommodated.
The difference between these two — 6213E-Z and 6213ZZCM — is design philosophy. The first is a general-purpose enhanced bearing with one shield. The second is a motor bearing with double shields and motor-specific clearance.
Brand-Specific Variations
SKF, FAG, NSK, NTN, and Timken use slightly different conventions for some suffixes. The same physical bearing might be:
For a deeper look at how the major brands compare, see SKF vs FAG Bearings — Which Should You Choose?.
Don't Guess Suffixes When Replacing
When replacing a bearing, match every suffix exactly. The original specification accounted for sealing, clearance, cage material, and internal design for a reason. A 6205-2RS1-C3 in a hot motor is not interchangeable with a plain 6205 — the clearance difference alone will cause premature failure as the motor heats up.
If the suffix on your old bearing has worn off and you can't read it, look it up by the equipment manufacturer's spec or by the bearing manufacturer's catalog. Don't guess.
Look Up Any Bearing
If you have a bearing part number with suffixes you don't recognize — especially brand-specific ones — search it on Partmatch. Paste any bearing number and get the verified equivalent across SKF, FAG, NSK, NTN, Timken, and 30+ other manufacturers, with provenance attribution on every result.
Search any bearing part number →
For more on bearing nomenclature:
- How to read a bearing part number
- What does 2RS mean on a bearing?
- SKF vs FAG bearings — which should you choose?
Partmatch provides verified bearing cross-references across SKF, FAG, NSK, NTN, Timken, and 30+ other manufacturers. Search any part number to find equivalents with verified provenance.